USC Dornsife Scientific Diving: The Guam and Calayan Rails

In the Pacific, a genus of birds known as Gallirallus has evolved on various islands forming twelve distinct modern species, endemic to different islands ranging from Okinawa all the way to New Zealand. Among these species are the Calayan rail (Gallirallus calayanensis) also known as the piding, and the Guam rail (Gallirallus owstoni) also known as the koko. Although they are closely similar birds physiologically, threats to their survival differ due to the details of human impact – specifically habitat availability and predation by invasive species.

Guam rail or koko. (Photo by Jim Haw)

On our first day in Guam, we visited the Department of Agriculture where we were fortunate to encounter several endangered species including the Guam rail. A tropical depression passing to the south of Guam and greater restrictions on entering the captive enclosure prevented us from visiting the breeding cages, so our meet and greet began in a back room of the office building.

Excitement filled the room as a local wildlife biologist in the Department of Agriculture and Wildlife Resources (DAWR), brought out a female koko, one of five birds that DAWR has imprinted for educational purposes. We observed her beautiful plumage and graceful stance as she gobbled up mealworms, her favorite treat.

Author feeding Guam Rail. (Photo by Jim Haw)

Enthralled by the little bird, we took many photos and jumped at the opportunity to feed and interact with the bird. Meeting the koko brought my previous knowledge of the species to life, making the rare encounter even more meaningful.

Like many endemic island species, the Guam rail has suffered much damage as a result of modern human impact. Historically, the Guam rail has been a symbol for the island nation and Chamorro native people. Despite the beloved status of this bird, the rails died off over several decades in an onslaught of brown tree snakes (Boiga irregularis), another species that we were able to encounter.

The surprisingly docile juvenile brown tree snake. Adults of five to eight feet in length are so aggressive that even seasoned wildlife biologists are reluctant to handle these mildly venomous snakes. (Photo by Jim Haw)

Researchers speculate that the snake arrived shortly after WWII -- stowing away on a cargo ship, possibly from Papua New Guinea, where the snakes are native (Department of Agriculture). As an alien species, the brown tree snakes thrived in Guam due to lack of natural predation, and it quickly demolished the rails, a flightless source of easy protein. In 1983, G. owstoni populations were estimated around 2,000 individuals; merely four years later, fewer than 100 were left (Bird Life International).

The Guam rail was declared extinct in the wild as of 1987 (Bird Life International). According to the U.S. Fish and Wildlife Services, major efforts have been made in captive breeding programs recently that have resulted in several reintroduction attempts to wild habitats on Cocos Island, south of Guam, and Rota, north of Guam.

The author and class interacting with a juvenile brown tree snake. (Photo by Jim Haw)

However, these reintroductions have been hit and miss. Over a dozen zoos across the mainland United States have established successful captive breeding programs. Today, there are an estimated three hundred Guam rails alive worldwide (U.S. Fish & Wildlife Service).

Far from the rollercoaster-like story of the Guam rail is the history of the endemic Calayan rail, found on the northern Filipino island of Calayan. Only declared a species in 2004, the Calayan rail is relatively successful in its favored coralline limestone habitat.

However, due to its small population of only 202 individuals as of 2006, the species is listed under the IUCN as vulnerable (Bird Life International). Although the Calayan rail has not been decimated by alien species like its relative on Guam, it is no stranger to threats. Mainly, the Calayan rail suffers from habitat loss due to human encroachment.

Calayan Rail. (Photo by C. Oliveros)

Even though humans minimally populate Calayan, their impacts are still felt across the island’s ecosystems. Conversion of habitats to croplands, unregulated subsistence logging, road building, and trapping -- both accidental and intentional for domestic trade, all contribute to Calayan rail losses (Calayan Rail Fact Sheet). Additionally, human population growth increases the likeliness of increased populations of cats, dogs, and rats, which can also prey upon the Calayan rail (Bird Life International).

Similar to the recent push for conservation of the Guam rail, there been a noticeable increase in Calayan rail conservation. The Sangguniany Bayan of Calayan passed Municipal Ordinance No. 84 stating that the capture, sale, possession, and collection of the Calayan rail is prohibited with violations subject to expensive fines (Calayan Rail Fact Sheet). In addition, the Isla Biodiversity Conservation established the Calayan Rail project, which increases awareness about conservation efforts across the Philippines and its schools. Also, the Calayan municipality and surrounding waters have been proposed as a protected area, which would greatly benefit the Calayan rail species (Calayan Rail Fact Sheet).

As both Guamanian and Filipino societies continue to change, so too will the stories of the rails. Because wildlife and mankind are so closely linked, the consequences of our actions must be examined carefully, especially when dealing with such fragile populations as these. Not only are these birds native to regions rich in biodiversity, their stories serve as warnings as to what damaging effects human actions can have on wildlife if left unchanged.

About the Author: Dawnielle Tellez is a sophomore Environmental Studies major in the USC Dana and David Dornsife College of Letters, Arts and Sciences. Dawnielle has a strong interest in marine science and looks forward to pursing a career in veterinary medicine with a specialty in marine mammal care.

Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.

Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg,, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

ABOUT THE AUTHOR(S)

Jim Haw

Dr. Jim Haw is Ray R. Irani Professor of Chemistry and director of the Environmental Studies Program in the USC Dana and Dornsife College of Letters, Arts and Sciences. He is also a scientific, technical and recreational diver.

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